New to TFP Method - Can't keep Chlorine up b/c CYA is high

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T

TruckStopWaitress

Member
Jul 25, 2022
9
Indianapolis
Pool Size
19000
Surface
Vinyl
Chlorine
Liquid Chlorine
Hi - I'm new to the methodology. Up till a couple weeks ago I've been using dichlor (Leslie's Chlor-Brite) to shock and also have an AutoChlorine Inline Feeder that uses 3" pucks. I recently bought the TF Pro test kit but am having trouble keeping chlorine up due to high CYA (at least that's my suspicion as to the main cause; could be multiple factors at play for all I know).
My numbers as of ten minutes ago:

FC= 1.0
CC= 0.5
TC= 1.5
pH= 7.2
CH= 400
TA= 210
CYA= 90
Water temp= 86 F
Air temp= 89 F
Water appearance= very slightly cloudy, no signs of visible algae

Thanks!
 
Thanks for your reply.

Yes, I'm positive I used 25ml for the TA test. When I tested it a week ago it was at 180.

For the Overnight Test, does it matter that I have an opaque gray autocover? I always close it at night. Should it be open for the purposes of this test?
 
Darn. I just realized I don't even have enough liquid chlorine on hand to get it up to 3ppm before nightfall.
If we were to assume that I'm losing more than 1ppm overnight and DON'T pass the OCLT, what would be my next steps? Would it be pointless to start the SLAM process tomorrow without getting my CYA lower beforehand? Will the TA of 210 prevent the SLAM from working?
We also leave for a five-day vacation on Friday, so that adds a wrench to the works. (grumble grumble)
 
With a CYA of 90, you should do the diluted test here, #8. It may, in fact, be higher.

www.troublefreepool.com

CYA - Cyanuric Acid Test

Cyanuric acid (CYA) is the chemical name for the product commonly called “pool water stabilizer” … Read more…
www.troublefreepool.com www.troublefreepool.com

Yes, a SLAM at CYA of 90 is really hard. Doable, but hard. Do you work from home?

Post up the diluted results and we'll put a strategy together.
 
Just tested CYA and chlorine (did not do OCLT bc I didn't have enough to get it up to 3ppm):
CYA (using the diluted test you linked) = 90
FC= 0.5
CC= 0.5
TC= 1.0

I do work from home! So that should make this slightly easier, yes?
Thank you for advice
 
We always round up to the next 10, so 45 is 50, doubled is 100.

You need to replace at least 40% of your water to remove the CYA.
 

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Thanks for your reply and my apologies for the long delay in responding. We got back from our vacation last night and of course the chlorine levels were at 0 this morning. So I'm starting the process of draining off (and concurrently replacing) approx 40% of the water in order to lower CYA.
I determined my outgoing water temp is 88 and incoming is 74 so I've got a submersible 1/2 HP pump in the deepest end of the pool (draining to my storm drain as I normally do when backwashing) and my regular garden hose filling at the skimmer.
Outgoing pump is draining at 5gal/min and incoming is filling at 5gal/2min so my plan is to periodically turn the pump off every hour for 30 minutes while keeping the incoming on at all times. Does this seem reasonable?
Also want to confirm that I should have my main pool pump equipment all turned off for the entire process? Many thanks!
 
With those water temperatures, you are doing it backwards. Cold water sinks. So add to the deep end and put the submersible pump on a step near surface.

Main pool pump off for the entire process.

Draining - Further Reading

www.troublefreepool.com www.troublefreepool.com
 
You want to fill at the lowest point and extract at the surface and at the greatest distance from the lowest point. Edit:Marty'd
 
Pumping from the deep and filling the shallow seemed counterintuitive to me, but I based it off this bit copied from the Draining section of the site:

"Pump from the deep end or near the surface?
To determine whether you pump from the deep end of the pool or from near the surface of the pool, depends on your fill and pool water characteristic.

Adding water to the deep end while pumping from a top step or near the surface is recommended if your fill water is much colder (>20F) then the pool water.

Put the pump in the deep end and fill from the shallow end if your fill water is nearly the same temperature as the pool water, you have a saltwater pool, or have very high CH. Put the fill hose in the skimmer, if you have one, in the shallow end."

Since the temperature difference in my fill and existing water was less than 20F (88-74=14) I figured I should put the pump in deep end. i.e. to me, the above indicates that I would only add water to the deep end if my fill water had a greater than 20 degree difference; so if my fill water were 68 or less I would follow the add water to the deep end/pump from the step. I'm confused as to why I'd follow the above direction with only a 14F temp difference.
 
You didn't include the PWTDS and the TWTDS....I did back of the napkin calcs...

Add to the deep, pump from the shallow, you will have less mixing. Turn your pool pump off.

(88 - (1200/165)) - (74-(500/165)) = 10

On liquid chlorine, in the midwest, typical TDS is 1000-1200...winter waters keep it about there. Most muni waters in the midwest, 500 is a reasonable TDS

If DeltaT is positive, then you want to fill at the lowest point and extract at the surface and at the greatest distance from the lowest point.
 
Last edited:
Yeah I think I see where I went wrong - it was in the order of operations for that equation. I assumed 800 for PWTDS and 200 for FWTDS but then I subtracted before division and came up with a negative number for the following equation: DeltaT = (PWT - PWTDS / 165) - (FWT - FWTDS / 165)
This would make more sense to me if written:
DeltaT = [PWT - (PWTDS/165)] - [FWT - (FWTDS/165)] which is more in line with how you utilized parentheses in your previous answer.

But aside from my mathematical error, how would one test for TDS at home? My TF-Pro kit has no way of measuring that from what I can tell.
 
TruckStopWaitress said:
But aside from my mathematical error, how would one test for TDS at home? My TF-Pro kit has no way of measuring that from what I can tell.
Click to expand...
Yeah, good ol' PEMDAS. You don't test for it. Except for this one thing, we don't use TDS in pool care. (I'll update the wiki)
 
Thanks for clearing that up.
Good news is that despite my backwards method of replacing the water, my CYA is down to 50 this morning so I can start the SLAM!

pH= 7.2
FC= 0
CC= 0
TC= 0
CH= 250
TA= 200
CYA= 50
Pool Temp= 84

According to the OldPoolMath page, my first order of business is adding 486oz of 10% LC to SLAM to get FC up to 20. Wish me luck.
 
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